The present invention relates to drywall tools for applying mastic and especially to extendable handles for use with drywall tools.
Drywall tools, such as flat finishing tools for applying mastic to drywall joints, are typically provided with extendable handles that permit the user to comfortably reach areas of the drywall near the floor or ceiling. Such handles comprise an inner tube that telescopes within an outer tube to change the length of the handle. The tubes may be reversibly locked together relative to each other to fix a variable length of the handle during use. In conventional drywall tools, the tubes are locked together by a pin located on the outer tube that alternately engages one of a series of holes along the length of the inner tube. The pin is positioned at one end of a rocking lever that is spring-biased to engage the pin in one of the holes of the inner tube and lock the inner and outer tubes together. To change the length of the handle, the user applies pressure to the other end of the rocking lever against the spring-bias with his thumb to disengage the pin from the hole and allow the tubes to telescope freely. Once the handle has been extended or shortened to its desired length, the user releases the switch, allowing the pin to engage the appropriate hole on the inner tube and fix the length of the handle.
Because the rocking lever must be operated by the user's thumb, such conventional locking mechanisms can be awkward and tiring to use. Furthermore, as the user actuates the rocking lever, his hand or fingers may inadvertently become caught in the locking mechanism. To prevent such injury, the rocking lever is typically enclosed by walls positioned on either side of the locking mechanism. However, these walls make it difficult to access the locking mechanism for cleaning and repair. Thus, there is a need for a flat finishing tool with an extendable handle that is simpler and safer to operate, and that has a locking mechanism whose parts are readily accessible for cleaning and repair.